Using 3d scanned textures
This blog post explains how to retopologize a mesh and bake the normal maps from the hi-polygon mesh to the low polygon mesh. This was exactly what I was looking for, but didn't know what the process was called (baking normal maps).

Another blog post that goes into greater detail on baking normal maps.

I would also like to thank @TARDIS Maker for pointing out that 3D scans could be done as a full on mesh and not only point clouds, AND for shining the light of retopologizing hi-res meshes. I had no idea this process existed.